Facebook on Tuesday launched a feature that allows users to lock down their Facebook accounts and perform malware scans if they suspect that their computers might be infected.

Facebook already uses internal scanners to detect spam and malicious messages that might have been sent from user accounts hijacked by malware.

When found, such accounts are temporarily locked down and their owners are asked to go through a multi-step account recovery process that involves downloading and running a malware scanner called McAfee Scan and Repair.

The new "malware checkpoints" feature will allow users who believe their computers might be infected with malware to initiate the account lockdown procedure themselves and perform an antivirus scan for free.

Users will be able to choose to scan their computers with McAfee Scan and Repair, a run-once anti-malware scanner, or with Microsoft Security Essentials, a full-featured antivirus product that must be downloaded and installed.

"If you are concerned that your device may have been infected by malware, you can visit http://on.fb.me/infectedMSE or http://on.fb.me/infectedMcA to be self-enrolled in either our Microsoft Security Essentials or McAfee Scan and Repair malware checkpoints," Facebook's security team said in a blog post.

The malware checkpoint feature will allow users to act proactively and not wait for Facebook's automated scanners to identify a threat, the security team said.

If users choose the McAfee Scan and Repair checkpoint they won't be able to unlock their account until the malware scan, whose progress is displayed on Facebook's website, is complete.

However, if users choose the Microsoft Security Essentials option they must manually certify, by checking a box on the website, that they downloaded, installed and performed a scan with the antivirus program before their account is unlocked.

Mac OS X users will be presented with a link to a page on Apple's support website from where they can download security updates and malware removal tools released by Apple.

However, they can also separately download the free Sophos Anti-Virus for Mac Home Edition from the AV Marketplace that Facebook launched in April.

"We hope that by making our technology available to more users, on demand, will help all the people who use our service keep their data and devices secure," the Facebook security team said.